Various printing devices include printers that accept individual sheets of pre-cut media or web printers that form images on a continuous web of print media. In a web printer, a continuous supply of media, typically provided in a media roller, is entrained onto rollers that are driven by motors. The motors and rollers pull the web from the supply roller through the printer to a take-up roller. As the media web moves along the media path, the imaging device forms images on the media web that may include text and graphics in one or more colors. Common embodiments of web printing systems include offset lithographic printing systems and inkjet web printing systems.
Installation of a media web in a printer to enable printing on the web requires a threading operation. A threading operation feeds a free end of the web media from the supply roller through the media path to the take-up roller prior to the commencement of printing. A threading operation can occur for various reasons. In some circumstances, a new media web replaces an exhausted media web supply. In other cases, breakage of a media web requires a remaining portion of the web roller that broke or a new web roller to be threaded through the media path. Because some media web printers use different media paths for different print modes, changes in the printing mode for a printer may necessitate a threading operation.
In a typical threading operation, a human operator pulls a free end of the media web through the media path and attaches the free end to the take up roller. Because the media paths in many web printers are long, the media path may make one or more turns through the printer. Manual manipulation of the media web in such printers can be tedious and time consuming. Some existing web printers include one or more manual switches that enable the operator to activate selectively motorized rollers positioned along the media path to assist in pulling the web through various portions of the media path. The selective activation of the motorized rollers still require the operator to pull the free end along and guide the web through the printer while engaging the switches to activate rollers as the free end approaches a still roller. If a switch is not located close enough to the free end of the web, the operator must travel back and forth between the switch and free end of the web. Thus, threading operations can be slow and require extensive operator interaction. Improvements in threading operations that enable more efficient threading of the media web would be beneficial.